Gamma rays are a form of high-energy electromagnetic radiation and require specialized detection methods due to their penetrating power. A Geiger counter is specifically designed to detect ionizing radiation, including alpha particles, beta particles, and gamma rays. This instrument uses a Geiger-Müller tube, which ionizes gas within the tube when radiation passes through it, creating an electrical current that can be measured and indicated, often as an audible click.
While X-ray film and photographic film can register high-energy radiation, they are not practical for direct detection of gamma rays in real-time scenarios. These films primarily capture images of radiation exposure over time rather than providing immediate readings. Photodiodes can detect light and other types of electromagnetic radiation, but they are not effective for gamma rays due to their energy levels and the nature of the detection mechanism. Therefore, the Geiger counter is the appropriate and specialized tool for detecting gamma rays in various environments, making it the correct answer.